This invention relates to means for drivingly interconnecting a first assembly to a second assembly. In particular it relates to interconnecting the flywheel of a heavy construction vehicle to a hydrostatic transmission in the vehicle.
Interconnection of the power plant of a vehicle to the drive train of the vehicle presents a unique problem in alignment since the drive train which usually includes a transmission is usually a separate unit from the vehicle engine. Since any misalignment between the power plant and the vehicle drive train results in friction losses during operation of the power plant and drive train, minimization of the misalignment is not only desirable, but necessary. In certain instances it has been found appropriate to utilize flexible or resilient members between the power plant and the vehicle transmission. However, such flexible members can impart an undesirable load to the associated bearings causing premature failure.
Flexible or resilient interconnecting means between the vehicle engine and the vehicle drive train also present problems in assembly of the two components. It is generally necessary to provide access to both sides of the flexible member if the flexible member is to be disassembled in the field. However, since the flexible member may be molded, it may be more appropriate to provide a disassembly point on either side of the flexible member. In any event, the flexible member is an expedient that has not proved in all cases to be appropriate.
Space and weight are generally problems in the construction of any type of vehicle. The drive train length should therefore be made as short as possible commensurate with with vehicle design without loss of efficiency. It is also important in internal combustion engines to include a large rotating mass to provide momentum to the engine crank shaft. This can be accomplished in any one of a number of ways. For example, in an aircraft engine the mass may be in the form of a propeller. In certain types of heavy equipment, the mass may be a large rotating portion of the drive train. In many engines it is appropriate to include a flywheel affixed to the crank shaft. In those engines which include a flywheel affixed to the crank shaft, connection of the engine flywheel to the transmission has been accomplished in some installations through the use of the resilient flexible fitting noted above. Since the entire drive train is generally separated from the engine at a point proximate the flywheel, it has proved appropriate to form the flywheel housing in two portions so that the drive train and transmission may be separated coincident with the separation of the flywheel housing. This type of separation may introduce a misalignment problem between the transmission and the flywheel. Accordingly, such misalignment should be readily absorbed in the interconnecting drive member. If the interconnecting drive member were such that separation of the transmission required a separate effort on the part of the separating mechanic to disconnect the interconnecting drive member, the length which is important, and in some instances critical, would of necessity be increased. Accordingly, it is appropriate to design the interconnecting drive member with the shortest possible length.
In providing a short length interconnecting link between a flywheel and a transmission, it would be desirable for the interconnecting link to remain with either the flywheel or the transmission during disconnection of one from the other. As a corollary function to a retention means to meet this need, it has been found that the retention means may prevent a sheared interconnecting shaft from disassociating itself from the flywheel in the event of failure of the shaft.
Finally, in design of any machinery element, it is appropriate to prevent errors which may take place during assembly. Such errors in a non-symmetrical shaft member which has similar but not identical construction at both ends may occur when the mechanic inadvertently places the non-symmetrical drive shaft in the machine in the wrong orientation. The most common way to prevent an assembly error is to insure that the two ends of the shaft are visually dissimilar. This has the inherent drawback that the assembling mechanic may be forced to refer to an assembly drawing to determine the proper orientation of the part. A second means for insuring proper orientation at assembly is to utilize similar structure at either end of an interconnecting shaft but to differ the shaft dimension so that assembly is only possible in one orientation. This type of structure results in the drawback that a minor dimension difference could result in a mechanic attempting to force assembly of the structure.
The most appropriate type of structure is a symmetrical interconnecting drive shaft so that installation is not hampered by different shapes or different dimensions. In short the mechanic may place the shaft in either orientation without fear of failure.